Method and Device for Optimizing Combustion in a Power Plant

ABSTRACT

Methods and devices for optimizing combustion of fuel in a combustion chamber of a power plant are provided. A real concentration distribution of a material and/or a real temperature distribution in the combustion chamber is measured in at least one dimension. The real concentration distribution and/or temperature distribution is evaluated and a combustion of fuel is controlled such that a symmetric concentration distribution and/or temperature distribution in the at least one dimension arises. During the evaluation at least one characteristic of the symmetry of the real concentration distribution and/or temperature distribution is determined, and during the controlling at least one control parameter is changed depending on the at least one characteristic.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International ApplicationNo. PCT/EP2009/067627 filed Dec. 21, 2009, and claims the benefitthereof. The International Application claims the benefits of EuropeanPatent Application No. 08172545.9 DE filed Dec. 22, 2008. All of theapplications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The invention relates to a method and a device for optimizing thecombustion of fuel in a combustion chamber of a power plant, in which areal concentration distribution of a substance and/or a real temperaturedistribution is measured in the combustion chamber.

BACKGROUND OF INVENTION

It is the basic object in the case of power plants to monitor thecombustion, which occurs in a combustion chamber of the power plant, forexample a boiler with a square surface area of 10 meters by 10 meters,over the largest possible area in order to be able to derive therefromthe necessary variables for optimizing the combustion process.

For example, absorption spectroscopy is a known method. Acousticpyrometry is a known alternative measurement technique. Absorptionspectroscopy and acoustic pyrometry can only measure mean values along aline through the boiler chamber or combustion chamber.

The CAT (computer-aided tomography) measurement technique is known forcalculating the temperature- and concentration distribution in a planeof a combustion chamber from measured mean values at different locationsof the combustion chamber of a power plant.

SUMMARY OF INVENTION

It is an object of the invention to develop a further optimization ofthe combustion in a power plant.

The object is achieved by methods and devices as claimed in theindependent claims. Advantageous developments are described in thedependent claims.

The method for optimizing the combustion of fuel in a combustion chamberof a power plant comprises the steps of: measuring a real concentrationdistribution of a substance in the combustion chamber in at least onedimension, evaluating the real concentration distribution, andcontrolling the combustion of the fuel such that a symmetricconcentration distribution of the substance is created in the at leastone dimension.

Alternatively, or in addition thereto, the method for optimizing thecombustion of fuel in a combustion chamber of a power plant comprisesthe steps of: measuring a real temperature distribution in thecombustion chamber in at least one dimension, evaluating the realtemperature distribution, and controlling the combustion of the fuelsuch that a symmetric temperature distribution is created in the atleast one dimension.

More particularly, within the scope of the method, at least onecharacteristic for the symmetry of the real concentration distributionand/or temperature distribution is established during the evaluationprocess and at least one control parameter is modified depending on theat least one characteristic during the control process.

Accordingly, a device for optimizing the combustion of fuel in acombustion chamber of a power plant comprises an apparatus for measuringa real concentration distribution of a substance in the combustionchamber in at least one dimension, an apparatus for evaluating the realconcentration distribution, and an apparatus for controlling thecombustion of the fuel such that a symmetric concentration distributionof the substance is created in the at least one dimension.

Alternatively, or in addition thereto, a device for optimizing thecombustion of fuel in a combustion chamber of a power plant comprises anapparatus for measuring a real temperature distribution in thecombustion chamber in at least one dimension, an apparatus forevaluating the real temperature distribution, and an apparatus forcontrolling the combustion of the fuel such that a symmetric temperaturedistribution is created in the at least one dimension.

In the case of a first advantageous development of the method,two-dimensional concentration distributions and/or temperaturedistributions are measured during the measurement process and at leastone one-dimensional concentration distribution or temperaturedistribution is calculated therefrom during the evaluation process.

In the case of a further advantageous development of the method, thereal concentration distribution and/or temperature distribution isdecomposed into a number of sections during the evaluation process andthe combustion is controlled such that a symmetric concentrationdistribution or temperature distribution is created in each section.

In other words, an at least one-dimensional, but preferablytwo-dimensional, distribution of the temperature and/or concentration ofat least one substance is generated on the basis of known measurementtechniques. The distribution measured thus is used to calculateone-dimensional and mathematical distributions or curves along an axisor along an axis section. Characteristics are preferably established forthe distributions, which characteristics ascertain or describe thesymmetry or asymmetry (skewness) of the mathematical distribution.Depending on the characteristics, suitable regulating units, such ase.g. metering hoppers for coal or air-control flaps, are trimmed suchthat there is a symmetric distribution along each axis. If there are anumber of mathematical distributions along one axis, the observed axesare subdivided into suitable axis sections and the above-describedoptimization is then performed for each of the sections.

The described procedure and the associated device allow a largelyhomogeneous and hence low-pollutant combustion with automatic adaptationof the regulating parameters.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following text, an exemplary embodiment is explained in moredetail on the basis of the attached schematic drawings, in which:

FIG. 1 shows an exemplary embodiment of the device,

FIG. 2 shows an exemplary embodiment of the method, and

FIG. 3 shows, by means of grayscale values, graphs of the distributionsof CO and O₂ in a measurement plane of the device as per FIG. 1 beforeand after an optimization.

DETAILED DESCRIPTION OF INVENTION

FIG. 1 illustrates a combustion chamber 10 of a coal power plant (notillustrated in any more detail), in which a coal fire burns duringoperation of the coal power plant. Here, the combustion chamber 10contains fuel—coal—together with associated fuel gases, flames 11 andexhaust gases.

Two measurement planes 12 and 14 are provided in the combustion chamber10, on the edge of which planes there are measurement instruments 16,which are respectively spaced apart from one another. Two measurementinstruments 16 in each case allow a measurement along a line in theassociated measurement plane 12 and/or 14, wherein e.g. theconcentration of the substances O₂ (oxygen) and CO (carbon monoxide) canbe measured with the aid of the measurement instruments 16 and anassociated evaluation apparatus 18.

Furthermore, the measurement instruments 16 and the evaluation apparatus18 can be used to establish the temperature distribution in theassociated measurement plane 12 and/or 14. The measurement in this caseis based on a combination of measurement technique and CAT calculation.

Via a data bus 20, the evaluation apparatus 18 is operationally coupledto an optimization apparatus 22, an operating apparatus 24, and acontrol apparatus or control and protection system 26. The realconcentration distributions and temperature distributions established bythe evaluation apparatus 18 are used via the operating apparatus 24 suchthat the optimization apparatus 22 is used to generate suggestions foroptimizing the combustion and these suggestions can be used in thecontrol apparatus 26. This optimizes the flames 11 burning in thecombustion chamber 10, in particular in respect of low emission ofNO_(x)(nitrogen oxide).

For the purposes of optimization, the optimization apparatus 22evaluates the measured, real concentration distributions and controlsthe combustion such that a symmetric concentration distribution of theoxygen and carbon monoxide substances is generated along at least oneaxis or in at least one dimension.

The associated method is illustrated in FIG. 2. It comprises the step 28of measuring the concentration distribution of at least the O₂ and COsubstances in the aforementioned measurement planes 12 and 14. In step30, the temperature distribution is established in these planes.

This input data is used in step 32 to evaluate one-dimensional andmathematical distributions or curves, as well as associatedcharacteristics for the symmetry or asymmetry of the distributions, fromthe concentration distributions. Furthermore, the distributions orcurves are decomposed into a number of sections with their own,associated distributions in step 32.

Subsequently, on the basis of these investigations, an optimization ofthe combustion is carried out in step 34 to the effect that symmetricconcentration- and temperature distributions are created. These can bemonitored in the measurement planes 14 and 16, and so overall thiscreates a closed-loop control circuit to the step 28.

Although the measurement as per steps 28 and 30 could evaluate thousandsof features or items of information relating to the combustion, it isdeliberately only a very small section or part of this information thatis processed in the described procedure. Otherwise it would not bepossible to achieve an expedient cost/use ratio.

The evaluation is carried out on the basis of three basic assumptions orthree basic simplifications: only direct measurement values, moments,and gradients of the measurements are utilized. Thus, in particular, thedistribution tomography of the measured concentrations and temperaturesis reconstructed on the basis of, in particular, 20 to 25 points ofintersection of the measurements. These direct measurement values aredescribed as feature vectors. Furthermore, the underlying differencevalues between these direct measurement values are used and, if desired,intermediate values can be established on the basis of interpolation.

In order to obtain distributions in each desired direction, the first tofourth moment are established along the horizontal, the vertical, andboth diagonals of each measurement field, i.e. of each field between thepoints of intersection. The moments are established on the basis of theprofiles or distributions along each measurement direction or dimension.The first and second moment represent the mean value and the variance ofa distribution. The third and fourth moment represent the skewness andkurtosis of a distribution. The skewness is a measure of symmetry orlack of symmetry. The kurtosis is a measure of whether the distributionis peaked or shallow compared to a normal distribution or Gaussiandistribution.

Furthermore, the gradient of the mean value is established in eachmeasurement field. The magnitude or value of the gradient providesinformation (e.g. illustrated as an arrow in the respective measurementfield) as to where peaks or concentrations are located in thedistribution. FIG. 3 shows the result of the optimization of thecombustion undertaken thus. FIG. 3 clearly shows the largely symmetricdistribution of CO and O₂ in the measurement plane 12 after theoptimization.

1.-8. (canceled)
 9. A method of optimizing combustion of fuel in a combustion chamber of a power plant, comprising: measuring a real concentration distribution of a substance in the combustion chamber in at least one dimension; evaluating the real concentration distribution; controlling a combustion of fuel such that a symmetric concentration distribution of the substance is created in the at least one dimension; determining at least one characteristic for a symmetry of the real concentration distribution during the evaluating; and modifying at least one control parameter depending on the at least one characteristic during the controlling.
 10. The method as claimed in claim 9, wherein two-dimensional concentration distributions are measured, and wherein at least one one-dimensional concentration distribution is calculated there from during the evaluating.
 11. The method as claimed in claim 9, wherein the real concentration distribution is decomposed into a plurality of sections, and wherein the combustion is controlled such that a symmetric concentration distribution is created in each section.
 12. The method as claimed in claim 10, wherein the real concentration distribution is decomposed into a plurality of sections, and wherein the combustion is controlled such that a symmetric concentration distribution is created in each section.
 13. A method of optimizing combustion of fuel in a combustion chamber of a power plant, comprising: measuring a real temperature distribution in a combustion chamber in at least one dimension, evaluating the real temperature distribution; controlling a combustion of fuel such that a symmetric temperature distribution is created in the at least one dimension; determining at least one characteristic during the evaluating for a symmetry of the real temperature distribution; and modifying a control parameter during the controlling depending on the at least one characteristic.
 14. The method as claimed in claim 13, wherein two-dimensional temperature distributions are measured, and wherein at least one one-dimensional temperature distribution is calculated there from during the evaluating.
 15. The method as claimed in claim 13, wherein the real temperature distribution is decomposed into a plurality of sections, and wherein the combustion is controlled such that a symmetric temperature distribution is created in each section.
 16. The method as claimed in claim 14, wherein the real temperature distribution is decomposed into a plurality of sections, and wherein the combustion is controlled such that a symmetric temperature distribution is created in each section.
 17. A device for optimizing combustion of fuel in a combustion chamber of a power plant, comprising: a measuring device for measuring a real distribution in a combustion chamber in at least one dimension; an evaluation device for evaluating the real distribution; a control device for controlling a combustion of fuel such that a symmetric distribution is created in the at least one dimension.
 18. The device as claimed in claim 17, wherein the measuring device measures a real concentration distribution of a substance in the combustion chamber, the evaluation device evaluates the real concentration distribution, and the control device controls the combustion of fuel such that a symmetric concentration distribution of the substance is created in the at least one dimension.
 19. The device as claimed in claim 18, wherein two-dimensional concentration distributions are measured, and wherein at least one one-dimensional concentration distribution is calculated there from.
 20. The device as claimed in claim 18, wherein the real concentration distribution is decomposed into a plurality of sections, and wherein the combustion is controlled such that a symmetric concentration distribution is created in each section.
 21. The device as claimed in claim 17, wherein the measuring devices measures a real temperature distribution in the combustion chamber; the evaluation device evaluates the real temperature distribution; and the control device controls the combustion of the fuel such that a symmetric temperature distribution is created in the at least one dimension.
 22. The device as claimed in claim 21, wherein two-dimensional temperature distributions are measured, and wherein at least one one-dimensional temperature distribution is calculated there from.
 23. The device as claimed in claim 21, wherein the real temperature distribution is decomposed into a plurality of sections, and wherein the combustion is controlled such that a symmetric temperature distribution is created in each section. 